Advanced Math/Height

Advertisement


Question
The distance at which an object falls varies as the square of the time of falling.  A rock dropped from a window 35 feet 1 inch hits the ground in 1. 5 seconds.  A rock dropped from a bridge hits the water in 4.5 seconds.  Calculate height of bridge.  Thanks.

Answer
"The distance at which an object falls varies as the square of the time of falling."
That means the equation relating distance and time has the form
  d = kt˛
where d and t are the distance and time, respectively, and k is a constant.

"A rock dropped from a window 35 feet 1 inch hits the ground in 1. 5 seconds."
t = 1.5 sec
d = 35 feet 1 inch = (35 + 1/12) feet = 421/12 feet

Use the first equation to determine k:
421/12 = k(1.5˛)
k = (421/27) feet per second˛

"A rock dropped from a bridge hits the water in 4.5 seconds."
d = (421/27)(4.5˛) = 315.75
The height of the bridge is 315.75 feet.

Advanced Math

All Answers


Answers by Expert:


Ask Experts

Volunteer


Janet Yang

Expertise

I can answer questions in Algebra, Basic Math, Calculus, Differential Equations, Geometry, Number Theory, and Word Problems. I would not feel comfortable answering questions in Probability and Statistics or Topology because I have not studied these in depth.

Experience

I tutor students (fifth through twelfth grades) and am a Top Contributor on Yahoo!Answers with over 24,000 math solutions.

Publications
Co-author of An Outline of Scientific Writing: For Researchers With English as a Foreign Language

Education/Credentials
I have a Bachelor's degree in Applied Mathematics from the University of California at Berkeley.

Past/Present Clients
George White Elementary School. Homework Help program at the Ridgewood Public Library, Ridgewood, NJ. Individual students.

©2016 About.com. All rights reserved.